1. Field of the Invention
This application is generally directed towards pressure valves, and more particularly to a valve for inflatable tires.
2. Description of Related Art
Automotive rollover accidents due to tire blowouts are a major concern in the automotive, trucking, bussing and racing industries. Most recently the Firestone/Ford Explorer rollover problems have been of major concern to the public and industry, and have been at least partially attributed to tire blowouts. In addition to the bad publicity, the lost business, the loss in public good will and confidence, and the high costs of tire and automobile recalls may represent major financial costs to tire and automobile manufacturers. Thus any improvement in actual or publicly perceived tire quality would be a benefit.
The tire inflation valve, which is likely to be the least expensive part of any vehicle, is one potential cause of catastrophic tire failures. This is because the valve stem of the tire inflation valve necessarily protrudes from the metal (for example steel or aluminum) wheel to enable inflation and deflation of the tire by the operator or service person. The protruding valve stem contains the valve sealing surface near the tip of the valve stem. This is so that the control actuator of the valve sealing surface may be accessed by the inflation nozzle that is applied to the tip of the valve stem. As a result of the location of the sealing surface, any damage to the valve stem that occurs below the level of the valve sealing surface results in sudden and complete deflation of the tire. Any vehicle that loses pressure in any one of its tires results in an unbalanced condition that adversely affects the handling of the vehicle. Such loss of handling efficiency may result in a loss of control of the vehicle by the operator, with understandable bad consequences to the operator, passengers or bystanders. Such loss of control instances may also represent a large economic loss or injury to the vehicle operators and to anybody else who is involved in the incident, for example bystanders.
The commonly used valve stems in automotive wheels may be rubber molded tubes that surround threaded brass valve bodies into which valves are screwed. The valve stems are designed to be inserted through the metal wheel rim from what will be the inside of the tire. If the portion of the tire valve stem that protrudes from the metal wheel impacts an object such as a rock or a curb, the portion of the tire valve stem that is torn or ripped off may contain the valve body with the sealing surface, and thus result in sudden tire deflation. In addition, an impact may completely rip the entire valve stem out of the steel wheel rim, thus also resulting in sudden tire deflation, and thus provoking a potentially life-threatening incident. Such damage and impact may also be due to acts of vandalism such as striking the very exposed valve stem with a knife or hammer. The damage may result in immediate loss of tire pressure, which may be easily noticed, or it may result in a weakened valve stem, that is not easily noticed, which weakened valve stem may suddenly rupture during high speed driving, resulting in a loss of control incident.
The extent of this problem may be seen in the attempts made to prevent sudden loss of tire pressure in the NASCAR race circuit. It is known that at the high speeds the typical racecar tire filled with nitrogen may have steel valve stem ruptures or failures that may occur upon any substantial contact with another car, side barriers or curbs. As a result some racecars have tires that contain a separately inflated inner tire so that the loss of pressure in a valve stem rupture accident is not complete, and thus the driver may maintain control of the vehicle. However, the inner tire adds weight to the vehicle, and thus slows the car down and affects the ability to turn. In addition, the inner tire may only last a short time before it also deflates, is thus not a solution to the valve stem rupture sudden deflation problem.
The problem of sudden deflation is not simply a racecar or automobile collision problem, but may also occur during normal traffic instances, such as highway driving on hot road surfaces resulting in increased tire pressure and thus possible valve stem rupture at either a manufacturing flaw or the site of a prior cut or impact, such as by a rock. This is because, as noted above, that the valve stem may be made of rubber with a metal valve body near the external tip. Thus an increased gas pressure inside the tire may be transmitted to the hollow valve stem at the portion below the valve that is still outside the metal wheel, which due to previous damage or manufacturing defect may then rupture.
The valve stem may rupture even if it is not made of rubber. Brass or steel valve stems may be attached to the metal wheel rim using sealing rings and nuts on either or both of the outside and inside of the wheel. Such metallic valve stems are also subject to damage due to impacts, rocks and vandalism, and further may be susceptible to thermal expansion mismatch, corrosion, repetitive bending and vibrations which may cause stress cracking. These cracks and defects may be hidden from view on the inner surface of the valve stem, or at the juncture of the valve stem and metal wheel, until the valve stem suddenly breaks under the influence of some event and the tire pressure is abruptly lost.
The problem of accidental damage to inflation/deflation valves is not limited to automobile tires. Any inflated object may have a valve that when damaged may cause the object to suddenly lose pressure and deflate, often with serious repercussions. Pressurized vessels and tanks also may have external valves that allow for either pressurization or for venting. The possibility of damage to the external valve may result in loss of the contents of the vessel or tanks, with potential for substantial damage to the tank or the surrounding environment. Examples of such tanks or vessels include compressed natural gas tanks and tanker trucks, chemical tankers transporting or storing liquids such as acids, alkali materials, chlorine bleach, mercaptans, pesticides, herbicides, radioactive or industrial wastes, the accidental release of which would clearly be a major problem. Other gaseous materials include various petroleum gases, hydrogen sulfide, hydrogen cyanide, sulfur dioxide, and fluorcarbons, all of which may be regularly transported by truck or train tankers, or stored in tanks in the manufacturing plants, in the ordinary course of manufacturing business, but are also deadly to the environment if released. Thus the normal transportation and storage of liquids and gases may involve the use of valves of the type discussed herein for accessing and removing gases, and for pressurizing tanks with inert or ordinary gases for safe storage and transportation, and for improved speed of off loading of various liquid materials. Any of these valves may be damaged by collisions, corrosion, accidental impacts or other damage, and result in the inadvertent release of potentially hazardous materials.
Thus it would be a benefit to automobile tire users and users of pressurized vessels and tanks to provide a valve that does not open when damaged due to accidents, overpressure situations, manufacturing defects, or accidental impacts.
An illustrative embodiment of the valve disclosed herein describes a valve comprising a valve stem, a valve body coupled to the valve stem and having a valve sealing surface with a valve sealing element disposed proximate to the sealing surface. A portion of the valve body is disposed to seal the valve stem to an aperture in a chamber that has an inside surface and an outside surface, and there is an elastic material biasing the sealing surface with respect to the sealing element. The sealing surface, the sealing element and the elastic member are disposed inside the chamber.
Alternative arrangements of the first illustrative embodiment of the valve disclosed herein describe a valve stem that has a weakened portion disposed at a location of the valve stem outside of the chamber. The valve stem weakened portion may have a location that is further from the chamber compared to the portion of the valve body that is disposed to seal the valve stem to the aperture in the chamber. The elastic member may be disposed to urge or bias the sealing element against the sealing surface with a predetermined force. The elastic member may be sensitive to a pressure difference between the inside of the chamber and the outside of the chamber, and upon the pressure difference exceeding a predetermined level, the elastic member may cease to urge the sealing element against the sealing surface. There may be a second elastic member disposed to urge the sealing element away from the sealing surface with a predetermined second force that is less than the predetermined force of the elastic member, and greater than a force required to separate the sealing element from the sealing surface against the predetermined pressure difference between the inside of the chamber and the outside of the chamber, in the absence of the urging of the elastic member. The elastic member may be sensitive to the temperature in the chamber, and upon the temperature exceeding a predetermined level, the elastic member may cease to urge the sealing element against the sealing surface. The second elastic member may be disposed to urge the sealing element away from the sealing surface with a predetermined second force that is less than the predetermined force of the elastic member, in the absence of the urging of the elastic member.
There may further be a hollow tubular cap disposed upon the end of the valve stem most distant from the valve base that includes a member disposed to enable the valve actuator to displace the sealing element to a location removed from contact with the sealing surface, resulting in a normally open valve. The cap member may be temperature sensitive and/or pressure differential sensitive, and upon the temperature or pressure exceeding a predetermined level, the cap member ceases to displace the sealing element away from the sealing surface. The chamber may contain a compressed gas, a combination of gases, a pressurized gas in at least partly liquid form, a liquid material having at least one of an inert or a non inert pressurized gas, and/or a pressurizable fluid.
In another illustrative embodiment of the valve disclosed herein there is a tire valve that comprises a valve stem, a valve body coupled to the valve stem with a valve sealing surface, a valve sealing element disposed proximate to the sealing surface, a valve actuator disposed to change a position of the sealing element with respect to the sealing surface, a spring biasing (e.g.; pushing or pulling) the sealing element against the sealing surface. There is a portion of the valve body disposed to seal the valve stem to an aperture in a wheel disposed to have a pneumatic tire installed thereon. The sealing surface, the sealing element and the spring are all disposed inside the surface of the wheel, and the valve stem has a weakened location disposed further outside of the wheel as compared to the portion of the valve body disposed to seal the valve stem to the wheel.
Alternative arrangements of the second illustrative embodiment of the valve disclosed herein describe a spring that pushes the sealing element against the sealing surface with a predetermined force. The spring may be sensitive to a pressure difference between the inside of the wheel and the outside of the wheel, and upon the pressure difference exceeding a predetermined level, the spring ceases to push the sealing element against the sealing surface with the predetermined force. There may further be a second spring disposed to bias or urge the sealing element away from the sealing surface with a predetermined second force that is less than the predetermined force, and greater than a force required to separate the sealing element from the sealing surface against the tire pressure difference, in the absence of the pushing of the spring. The first spring may be sensitive to the temperature in the wheel, and upon the temperature exceeding a predetermined level, the spring may melt and/or lose spring strength, and ceases to urge the sealing element against the sealing surface. There may further be a second spring disposed to urge the sealing element away from the sealing surface with a predetermined second force that is less than the predetermined force of the spring, and greater than a force required to separate the sealing element from the sealing surface against a pressure difference between the inside and outside of the wheel, in the absence of the urging of the spring. There may be a hollow tubular cap disposed upon an end of the valve stem most distant from the wheel that includes a member disposed to enable the valve actuator to displace the sealing element to a location removed from contact with the sealing surface, resulting in a normally open valve. The cap member may be a temperature sensitive and/or a pressure differential sensitive element, and upon the temperature or pressure exceeding a predetermined level, the cap member ceases to displace the sealing element away from the sealing surface. The wheel may be filled with compressed air, nitrogen, an inert gas, a reactive gas, and/or a combination of gases.
In a third illustrative embodiment, there are disclosed means for controllably sealing a chamber having a hollow stem, a body coupled to the hollow stem and having means for sealing a sealing surface against a sealing element disposed proximate to the sealing surface. There are means for biasing the sealing surface with respect to the sealing element, and the sealing surface, the sealing element and the biasing means are disposed within the protection of the chamber.
Alternative arrangements of the third illustrative embodiment include that the stem has means for stem breakaway disposed at a location of the stem outside of the chamber. The means for biasing may include a spring, an elastic material, a magnetic field, a fluid pressure differential, a remotely monitored electronic device, a remotely controlled electronic device, a remotely monitored electromechanical device, and a remotely controlled electromechanical device, and may bias the sealing element against the sealing surface with a predetermined force. The means for biasing may be sensitive to a temperature and/or a pressure difference between a region inside of the chamber and a region outside of the chamber and may include a second means for biasing disposed to bias the sealing element away from the sealing surface with a predetermined second force that is less than the predetermined force. There may be an externally controllable actuator resulting in a normally open valve, and it may be temperature or pressure sensitive.